Beelzeburb, The Story More Than a Decade in the Making

[Beelzeburb]

Okay, so, well... let’s say I just happen to be the owner of a slightly used Holley 4010 square bore carburetor that flows 750 CFM. That should be a decent enough size for the 454 right?



The Holley owner’s manual warns not to use this carburetor with overdrive transmissions, but it shouldn’t make any difference to my COMPUSHIFT controlled one though. I only need the right cable driven Acculink TPS adapter, a low pressure FPR and it should be good to go. Anyone have recommendations for an intake manifold?

Well, while the Suburban takes a hiatus , perhaps you’d like to see some pictures of my Datsun now that it’s all together.



















Ha Ha! Just kidding about the carb. That Holley would be a step backward that I don’t want to take. I’ve been fiddling with the Suburban the whole time and there is no hiatus. Where we last left off I had been testing individual components to rule them out one-by-one.

So far:

Ignition and Voltage
I’d made sure the charging system was charging, I kept the battery fully topped up with voltage with the Battery Tender Plus, the starter worked fine, the cap and rotor were clean and the spark plugs and wires seemed okay. I’d replaced the coil because it was known to cause similar symptoms to what I had been experiencing if it failed (and it was pretty cheap). I had also replaced the ignition module because I’d accidentally fried the old one by hooking the wrong wires up to it.

Other Sensors and Motors
The 02 sensor was fully functional and I had properly expunged all exhaust leaks so that they couldn’t confuse the O2 sensor. The coolant temperature sensors all read properly, the TPS gave correct voltage output, and the A/C compressor wasn’t sending a signal when it shouldn’t have been.

Emissions
The EGR solenoid and valve both checked out properly when I tested them, the A.I.R. hardware had been removed and disconnected properly, also, the PCV valve was new. The evaporative emissions canister was hooked up correctly too. I even checked all of the vacuum lines for leaks and found none.

Fuel System
The new Walbro fuel pump was happily pumping away and remained solidly grounded to the frame. The fuel filter and flexible lines were new and I’d blown compressed air through the hard lines only to find no restriction. The new JET Performance fuel pressure regulator did it’s job properly and held around 14 psi at idle. The fuel injectors themselves sprayed in a nice, clean fan pattern and didn’t leak or drip when the engine wasn’t running. There were no fuel leaks around the throttle body, intake manifold or EGR valve.

This left very few items to check. I quickly ruled out the MAP sensor. It read the correct voltage for the altitude that I live at, and when 10 inHg was applied with a hand vacuum pump the output fell by 2V which was in spec. I set the timing again after finding the tan/black wire quick-disconnect. Next I checked the IAC motor. The pintle on them is known to build up a carbon deposit which can cause an erratic idle. The whole of the IAC motor and it’s associated passage were clean as a whistle. It didn’t make a noticeable difference to put the ECM in diagnostic mode, driving the pintle to the fully seated position and then removing the IAC plug, thereby closing off the idle air passage. I simply plugged it back in after that because the thing seemed to be doing its job.

While I had the spark plugs out to perform the compression test, I noticed that one of them was a little longer than the others (I had broken one plug on accident and bought a new replacement). AC Delco must have made a small change to their CR43TS plugs some time in the past six years. I went ahead and replaced all eight with the new style. All the new plugs were gapped to 0.035” as called for in the service manual. I also installed a new set of Crane Cams Fire Wire spark plug wires with 90° boots because I didn’t like the universal boots on the Carquest set I had been using. Still no noticeable change in performance.

At this point, the only items I could think of that hadn’t been tested or replaced were the distributor internals, the ECM/PROM and the fuel injectors themselves. If it wasn’t one of them then I was going to start retracing every single wire checking for continuity and resistance. That Holley carburetor is just an old one that my Dad had had on a shelf because he could never get it to run right. Maybe some day I’ll put it in a vehicle and sort it properly, but it won't wind up on the Suburban.

I researched, pondered and hypothesized. The distributor was a bit of a gamble, but the most likely suspect at this point. If my backwards wiring had killed an ignition module, could it have damaged the internal pickup coil too? Was my replacement ignition module slightly different than the one it had replaced? Hmmm.... I could have replaced the HEI module and pickup coil with correct AC Delco parts for roughly $70, but if I did, then would the notorious problems of the early external coil distributors finally catch up with me? Perhaps the reluctor or stator had worn out or the magnets were broken into multiple pieces? In the end I decided to bite the bullet and purchase a complete GMPP 1103952 distributor assembly even though I have rebuilt a few distributors before. It’s a drop in and comes completely assembled with cap, rotor and ignition module.



As a plus, the 1103952 doesn’t suffer from many of the problems that plagued the earlier model distributors. The price wasn't that bad either, less than $200 at the local Chevy dealership. The two distributors sure didn't look any different from the outside though.



After a little fiddling to get it lined up with the right tooth, it plunked down in place of the old dizzy. I only managed to eyeball the alignment again, but it fired up and idled at around 1300 rpm. It revved very crisply from off idle and sounded tantalizingly promising. Before the new distributor there had been some hesitation off idle and the RPMs hadn’t climbed quite as quickly with the transmission in park or neutral. Too excited to bother with getting the timing spot on, I hopped in and backed out of the driveway.

Lo and behold, there was torque. The Suburban wasn’t some limply accelerating, backfiring sputter machine anymore. It pushed me back hard in my seat, a sensation I’d never felt in such a heavy vehicle. You have to understand that when I drove the Suburban during High School, a 0-60 acceleration run lasted somewhere in the neighborhood of 20-25 seconds. I’d driven Econoline vans at a hotel that I’d worked at for two years. A couple of them were equipped with the turbo diesel engines, but the turbo lag was horrible. Even though my 240Z is fairly well modified and pushing about 100 more horsepower than it had originally, with the cam that’s in it nothing happens below 2500 rpm and the fun stuff happens above 5000 rpm. Nothing had prepared me for the immediate wave of torquey goodness that my big block could now provide. I had to come to a complete stop a few times just to feel that sensation again and again.

Since then the timing has been set once again to factory specs, 4° with the tan/black wire disconnected and it idles nicely. At WOT the O2 sensor reading is still in the correct range, and it maintains a constant 14 p.s.i. of fuel pressure at idle. It still has a problem starting without a shot of ether, but I'll figure that out eventually. I have replaced the oil pressure switch in case that was causing problems with the fuel pressure relay (the two are connected), but no change on that front yet. In the next couple of days I'll put in a noid light from the new set I ordered and make sure the injectors are getting a strong signal when the starter is cranking the motor over. I'm just happy that it finally runs right. There is no sputter, no backfiring and no hesitation whatsoever at any throttle position or RPM. It just goes. Oh, and it'll spin the tires from a dead stop on dry pavement too.